A particle-gamma angular-correlation measurement system for high counting rates

Abstract

A system employing four semiconductor detectors and four NaI(Tl) scintillation counters for particle-gamma angular-correlation measurements at high counting rates is described. Scintillation counter pulses are shaped into rectangular pulses of 200 ns duration in order to reduce pile-up effects, and a compensation circuit for gain variation with rate is used. A fast decision-making logic unit employing MECL 10000 I.C.'s controls data transfer into an on-line PDP-9 computer. Dead-time losses are measured using a pulse-pair generator simulating particle-gamma coincident pulses. In an experiment with 5–8 MeV protons and 0.5–2.5 MeV gamma rays at a counting rate of approximately 100 000 cps at each of the scintillation counters, the gamma-energy resolution (fwhm) was 6–9%, depending on gamma energy, and the time resolution (fwhm) was 1.8 ns. Plots of typical results are shown.